By TODD BISHOP, P-I REPORTER

Updated 10:00 pm, Monday, May 14, 2007

Microsoft Corp. put a new twist into its rivalry with open-source software Monday by getting specific about one of its most controversial claims -- saying that Linux and other free programs violate 235 of its patents.

Open-source advocates questioned Microsoft's motives, pointing out that the company didn't name the specific patents or technologies at issue. Analysts said it could cause companies to re-examine the open-source software they use, to determine their potential legal exposure.

However, Microsoft stopped short of saying that it would consider legal action against companies that use open-source software. Such a move would be a delicate proposition, because many corporate Linux users are also Microsoft customers.

Instead, Microsoft said it hopes to persuade more open-source technology vendors to enter intellectual-property licensing agreements similar to the one it struck last year with Linux vendor Novell Inc. That agreement included a provision protecting customers of both companies from patent-related litigation.

"We hope that we can resolve this issue through licensing," said Horacio Gutierrez, Microsoft vice president of intellectual property and licensing. "We feel that it is a lot more beneficial for everybody ... if the solution can be brought about by companies coming together and using mechanisms that have been in place in the technology world for many, many decades, and that's the licensing mechanism."

Open-source software is created by worldwide communities of programmers who freely share their work. Linux, the most prominent example of open-source programs, competes with Microsoft's Windows operating system, particularly on computer servers, and Microsoft has called it one of its biggest rivals.

Microsoft's assertions drew a strong response from some corners of the open-source world.

"If Microsoft believes that Free and Open Source Software violates any of their patents, let them put those patents forward now, in the light of day, where we can all evaluate them on their merits," wrote Larry Augustin, an investor who has been involved in a number of open-source companies and initiatives, on his blog. "If not, then stop trying to bully customers into paying royalties to use Open Source. It's time for Microsoft to put up or shut up."

Gutierrez said Microsoft does discuss those specifics in discussions with other companies, which it considers the appropriate forum.

Microsoft Chief Executive Steve Ballmer alluded previously to the company's belief that Linux violates its patents, but the company has never before been so specific. The company first gave the figure of 235 patents in an interview with Fortune magazine, published over the weekend.

In the short run, Microsoft's assertion could be a boon for Novell, because of Microsoft's covenant under that deal to refrain from suing companies that use Novell's Suse Linux, said industry analyst Dwight Davis, vice president at Ovum Summit.

"It's a risky strategy for Microsoft," Davis said. "It obviously has calculated that the downside it faces is severe enough that it's worth alienating a lot of open-source developers and a lot of customers who have embraced open source over the years."

The agreement with Novell dulled a long-standing rivalry. At the same time it came under fire from open-source advocates such as the Free Software Foundation, which develops the General Public License, a popular open source license used for the core of the Linux operating system.

The group's proposed version 3 of the license terms would prevent future deals of the kind struck between Microsoft and Novell, which also involved the companies agreeing to make their software interoperable.

Microsoft criticized the new version in its statement Monday, saying it "attempts to tear down the bridge between proprietary and open-source software that Microsoft has worked to build with the industry and customers."